Electronic keyboard instrument

Abstract

An electronic keyboard instrument for reproducing reflected sound generated by an acoustic piano and providing the feeling that sound is reflected and shifted. Left and right system sound signals are generated corresponding to the position of a depressed key on a keyboard. The sound signals are processed through a digital signal processor, a digital-to-analog converter and amplifiers. The processed sound signals are transmitted to left and right loudspeakers. The digital sound processor is composed of filters for extracting predetermined frequency components from each of the sound signals, delay elements for transmitting outputs from the filters with a delay of predetermined time, and adders for adding outputs from the delay elements to the original left and right system sound signals.

What is claimed is: 
     
       1. A method of producing sound in an electronic keyboard instrument comprising the steps of: providing a keyboard having a plurality of keys arranged in at least one row thereon;   detecting a position of each said depressed key on said keyboard and a speed of depression of each said depressed key;   generating center, left and right sound waveforms representing sound having a tone and a volume corresponding to the detected position and speed of depression of each said depressed key;   extracting a predetermined first frequency component from the right sound waveform transmitted from a sound waveform output means, delaying the first frequency component by a predetermined first time period and adding the delayed first frequency component to a delayed frequency component from the center sound waveform, delayed by a predetermined third time period, and the left sound waveform thereby producing a left synthesized waveform;   extracting a predetermined second frequency component from the left sound waveform transmitted from said sound waveform output means, delaying the second frequency component by a predetermined second time period and adding the delayed second frequency component to a delayed frequency component from the center sound waveform, delayed by a predetermined sixth time period, and the right sound waveform thereby producing a right synthesized waveform;   extracting a predetermined third frequency component from the center sound waveform transmitted from said sound waveform output means, and adding said third frequency component with a delayed frequency component from the right sound waveform, delayed by a predetermined fourth time period, and a delayed frequency component from the left sound waveform, delayed by a pre determined fifth time period thereby producing a center synthesized waveform; and   generating left, center, and right sound corresponding to said center, said left and said right synthesized waveforms, respectively.   
     
     
       2. An electronic keyboard instrument comprising: a keyboard having a plurality of keys arranged in at least one row thereon;   keyboard operation detecting means coupled to each of said plurality of keys, for detecting directly, upon depression of any said keys, a position of each said depressed key on said keyboard and a speed of depression of each said depressed key;   sound waveform output means, coupled to each of said detecting means, for generating a plurality of sound waveforms representing sound having a tone and a volume corresponding to the detected position and the detected speed of depression of each said depressed key;   sound waveform synthesizing means, said synthesizing means being coupled to said sound waveform output means,   wherein a first predetermined frequency component is extracted from a first waveform, said extracted frequency component is transmitted with a first time delay and combined with a second sound waveform and a delayed third sound waveform to form a left output sound signal;   a second predetermined frequency component is extracted from said a second waveform, said second extracted frequency component is transmitted with a second time delay and combined with said first waveform and a delayed third sound waveform to form a right output sound signal;   a third predetermined frequency component is extracted from a third waveform, said third extracted frequency component is combined with a delayed first sound waveform and a delayed second sound waveform to form a center output sound signal; and   three sound emitters are coupled to said synthesizing means and are arranged in a row substantially parallel to the at least one row of said keys, and one of said three sound emitters corresponding with a respective one of said plurality of waveforms for emitting sound corresponding to said plurality of synthesized waveforms.   
     
     
       3. An electronic keyboard instrument comprising: a keyboard having a plurality of keys arranged in at least one row thereon;   keyboard operation detecting means comprising two key sensors each having a light emitting element and a light receiving element and a stepped shutter, said detecting means being coupled to each of said plurality of keys, for detecting directly, upon depression of any said keys, a position of each said depressed key on said keyboard and a speed of depression of each said depressed key;   sound waveform output means, being coupled to each of said detecting means, for generating a right system sound signal, a left system sound signal and a middle system sound signal, representing sound having a tone and a volume corresponding to the detected position and the detected speed of depression of each said depressed key;   sound waveform synthesizing means comprising a plurality of filters, a plurality of delay elements and a plurality of adders, and said synthesizing means being coupled to said output means,   wherein a first filter extracts a first predetermined frequency component from said right system sound signal, said extracted frequency component is transmitted with a first time delay by a first delay element to a first adder, and said first adder combines (i) said extracted frequency component from said right system sound signal with said first time delay, (ii) said left system sound signal and (iii) said center system sound signal with a third time delay to form a left output sound signal;   a second filter extracts a second predetermined frequency component from said left system sound signal, said second extracted frequency component is transmitted with a second time delay by a second delay element to a second adder, and said second adder combines (i) said extracted frequency component from said left system sound signal with said second time delay, (ii) said right system sound signal and (iii) said center system sound signal with a sixth time delay to form a right output sound signal;   a third filter extracts a third predetermined frequency component from said center system sound signal, said third extracted frequency component is transmitted to a third adder, and said third adder combines (i) said extracted frequency component from said center system sound signal, (ii) said right system sound signal with a fourth time delay and (iii) said left system sound signal with a fifth time delay to form a center output sound signal; and   at least three sound emitters are coupled to said synthesizing means, a left sound emitter is arranged to the left of a center of the row of said keys, a right sound emitter is arranged to the right of the center of the row of said keys and a center sound emitter is arranged to the center of the row of said keys, for emitting sound corresponding to the left, the right and the center sound waveform data, respectively.   
     
     
       4. An electronic keyboard instrument according to claim 3, wherein said sound waveform output means comprises: sound waveform generating means for generating said first, second and third sound waveforms with a tone corresponding to the detected position and a volume corresponding to the detected speed of depression of each said depressed key; and   sound waveform adjusting means for adjusting the volume of said first, second and third sound waveforms generated by the sound waveform generating means, such that a volume of the sound emitted by a said sound emitter located closest to said detected position of the depressed key is louder than a volume of the sound emitted by a said sound emitter farthest from said detected position, and providing said first, second and third waveforms generated by said generating means with a sound volume corresponding to the detected position of depression of said depressed key.   
     
     
       5. An electronic keyboard instrument according to claim 4, further comprising: waveform memory means, coupled to said sound waveform output means, for storing prerecorded monaural sound data comprising a plurality of single monaural sound waveforms, one representing each sound produced by individual strings of an acoustic piano; and   said output means reads a single monaural waveform corresponding to each said depressed key from said memory means and generates and adjusts said first, second and third waveforms from each said single monaural waveform read from said memory means.   
     
     
       6. An electronic keyboard instrument according to claim 3, wherein said sound waveform synthesizing means includes a left waveform synthesizing means for synthesizing the left waveform, a center sound waveform synthesizing means for synthesizing a right waveform and a right waveform synthesizing means for synthesizing the right waveform, and each said synthesizing means comprising: a filter for extracting a corresponding said frequency component from a corresponding one of the left, the center and the right waveforms, by permitting only said corresponding frequency component to pass through said filter;   a delay element for delaying said corresponding frequency component by a corresponding time period;   and an adding element, coupled to the other two said synthesizing means for adding a said frequency component extracted from the other of said left, center and right waveforms and delayed by said other two synthesizing means thereby to produce a corresponding said synthesized waveform.   
     
     
       7. An electronic keyboard instrument according to claim 6, wherein the center sound emitter is located midway between said left and right sound emitters. 
     
     
       8. An electronic keyboard instrument according to claim 7, wherein each of said center, said right and said left sound waveform synthesizing means comprises: two said filters, for extracting two said corresponding frequency components from a corresponding waveform, one for each of the other two waveforms;   two said delay elements, one for delaying each of said two extracted frequency components by a corresponding time period;   and an adding element, coupled to each of the other two said synthesizing means, for adding all corresponding frequency components extracted from each of the other two of said waveforms and delayed by said other two synthesizing means thereby to produce a corresponding said synthesized waveform.   
     
     
       9. An electronic keyboard instrument according to claim 3, wherein said first predetermined frequency component has a frequency of at least about 500 Hz, the first time period is 10 ms, the second frequency component has a maximum frequency of about 300 Hz, the second time period is 30 ms. 
     
     
       10. An electronic keyboard instrument according to claim 6, wherein in the left waveform synthesizing means, a left said filter permits only frequencies of at least about 500 Hz to pass through, and a left said delay element delays a left said frequency component by a time period of 10 ms; and in the right waveform synthesizing means, a right said filter permits only a maximum frequency of about 300 Hz to pass through, and a right said delay element delays a right said frequency component by a time period of 30 ms.   
     
     
       11. An electronic keyboard instrument according to claim 6, wherein a plurality of said sound emitters are arranged in a row substantially parallel to the at least one row of said keys; said sound waveform output means generates a plurality of said sound waveforms, one for each of said sound emitters, representing sound having a tone and a volume corresponding to the detected position and the detected speed of depression of each said depressed key; and   a plurality of said sound synthesizing means, one for each said sound waveform, for producing a corresponding said synthesized waveform.   
     
     
       12. An electronic keyboard instrument according to claim 11, wherein each said synthesizing means comprising: a plurality of said filters, one said filter for each other sound waveform, for extracting a plurality of frequency components from a corresponding waveform;   a plurality of said delay elements, one said delay element for delaying each of said plurality of extracted frequency components by a corresponding said time period;   and an adding element, coupled to each of the other said synthesizing means, for adding all corresponding frequency components extracted from each of the other of said waveforms and delayed by each said other synthesizing means thereby to produce a corresponding said synthesized waveform.